Minimally invasive medical techniques are intended to reduce the amount of tissue that is damaged during interventional procedures, thereby reducing patient recovery time, discomfort, and deleterious side effects. To track the location of anatomical targets, implanted devices, and/or interventional instruments (including surgical, diagnostic, therapeutic, or biopsy instruments) within a patient anatomy, minimally invasive sensor systems may be used. In existing systems, electro-magnetic (EM) navigation may be used to track the movement of interventional instruments, implanted devices, or targets in a patient anatomy. Although EM navigation systems are useful for many procedures, they may be subject to magnetic interference from other equipment in the surgical suite. For example, a C-arm of a fluoroscopic imaging system or metal instruments may generate magnetic interference with EM navigation systems, causing unacceptable errors in the tracking of an interventional instrument. In other existing systems, optical fiber shape sensor systems may be used to track the movement of interventional instruments in a patient anatomy. Optical fiber shape sensor systems monitor the strain at various points along a single optical fiber to determine the shape of the optical fiber. From the shape of the single optical fiber, the pose (position and orientation) of the various points along the optical fiber can be derived. The error associated with the derived poses for the various points along the single optical fiber may increase with distance from the optical fiber interrogator due to error accumulation. Improved navigation systems and methods are needed for tracking interventional instruments, implanted devices, and anatomic targets in surgical environments.